The present invention relates to a bar supporting apparatus for a lathe (which will be simply referred to as a bar supporting apparatus hereinafter) which supports a long circular work piece such as a bar or tube which is subjected to lathe work (it will be generically referred to as a bar hereinafter in the present specification) on a extended line of a main spindle of an automatic lathe.
This type of the bar supporting apparatus is provided in the vicinity of the automatic lathe and rotatably supports a portion of a long bar projecting from a head stock in order to prevent the bar from generating rotation oscillation. For example, as shown in FIG. 28, the prior art bar supporting apparatus 100 comprises: a case 111 having a predetermined length; a guide tube 113 whose diameter is slightly larger than an external diameter of a bar 117 which is to be supported in the case 111; and a hydraulic unit 114 which supplies a large amount of oil for supporting the bar 117 in the guide tube 113, and it causes the bar 117 to float in the guide tube 113 by the dynamic pressure of the oil involved by rotation of the bar 117 so that the bar is rotatably supported. It is to be noted that the bar 117 is gripped by a chuck 125 of a main spindle 124 of the automatic lathe so as to be processed. Since the rear end of the case 111 is sealed to avoid leakage of the oil in the bar supporting apparatus 100, the bar 117 is inserted after moving the front end side (the automatic lathe side) of the case 111 to the side with a supporting base 115 on the rear side as a supporting point. After inserting the bar 117 into the case 111, the case 111 is returned to its original position to be supplied to the main spindle 124 side (FIG. 29 and FIG. 30).
Here, although the oscillation of the bar 117 can be suppressed all the more as a gap between the external diameter of the bar 117 and the guide tube 113 is smaller, the bar 117 oscillates due to rotation during processing, and a narrow gap hence disadvantageously causes the bar 117 to come into contact with the guide tube 113 to generate heat. Therefore, the optimum gap between the internal diameter of the guide tube 113 and the external diameter of the bar 117 is determined to be approximately 1 mm in case of the bar having the external diameter of not more than 30 mm; approximately 2 mm in case of the bar having the external diameter of 31 mm to 65 mm; and approximately 3 mm in case of the bar having the external diameter of 66 mm to 69 mm. The quantity of the gap is also a problem of design, and these are approximate values. Thus, the guide tube 113 is replaced in accordance with the external diameter of the bar 117, or a guide tube having a small diameter is provided on the inner side of the guide tube 113 so as to cope with the bar 117 having a different external diameter.
In this case, in order to set an optimum gap between the guide tube 113 and the bar 117, the inner peripheral surface of the long guide tube 113 must be processed so as to obtain a straight axial center with the high accuracy, but it is very difficult to accurately process the inside of the long guide tube 113 with the current processing technology such as boring. Further, although the processing must be carried out with low-speed rotation depending on the bar 117 which is a target of processing, the dynamic pressure to be generated becomes small even if an appropriate gap is formed between the bar 117 and the guide tube 113 in this case, and the bar 117 does not float by oil but comes into contact with the guide tube 113 to cause the oscillation or noise.
In addition, a bend of the bar 117 is remedied by a straightening machine in the final step of the manufacturing process even if the bar 117 is made of a mill scale material or a polishing material and the bend is straightened to some degree, but the slight deflection is generated by its own weight and the like because it is actually long. Therefore, it is very difficult to inspect the bend of the bar 117, and the bend is often missed in the inspection even if the bar 117 is actually bent. The slightly bent bar 117 has to be supported by the bar supporting apparatus 100. Thus, the bar 117 oscillates more than necessary to come into contact with the guide tube 113 depending on the bend of the bar 117 which can not be found in the inspection, or the bar 117 may be deflected to be brought into contact with the guide tube 113 by the centrifugal force in the high-speed rotation, even if the bar 117 is not bent thereby generating oscillation or noise.
As a countermeasure, there is developed a bar supporting apparatus 100A which does not use the guide tube. As shown in FIGS. 31 and 32, the bar supporting apparatus 100A mounts on a counter 118 a plurality of supports 119 each consisting of a bearing having oil supplying means at predetermined intervals. An upper support 119A and a lower support 119B of the support 119 are disposed to the respective halves of the bearing 123, and the bar is inserted and removed by oscillating the upper support 119A around an upper frame pivot 120. The upper support 119A opens and closes by using a cylinder 122. The bearing 123 has a diameter slightly larger than that of the bar 117 and supports the bar 117 by generating the dynamic pressure between itself and the bar 117 with a large amount of oil being supplied to the bearing surface. Thus, since the oil supplied from the hydraulic unit to the bearing 123 of the support 119 spatters or leaks, the entire apparatus is covered with a large casing, thereby enlarging the size of the apparatus. It is to be noted that a plurality of the supports 119 are provided on the counter 118 at predetermined intervals. The apparatus is assembled so that all the upper and lower bearings 123 disposed to the multiple upper and lower supports 119A and 119B provided at predetermined intervals can have the axial centers accurately matched with each other.
However, since the bearing 123 is split in two to be supported by the upper and lower supports 119A and 119B and others, the shapes of components of the bearing 123 are complicated and hard to be processed. Further, it is very difficult to perform accurate centering on all the bearings 123 disposed to the upper and lower supports 119A and 119B due to an attachment error and others of the respective supports.
Moreover, when the gap between the bar 117 and the half bearing 123 is narrowed to approximately 1 mm or less, the bar 117 can be further rotated with no noise. However, since the upper and lower supports 119A and 119B are separately disposed, they can not be disposed to the same accurate straight axial center but attached with the respective axial centers being slightly shifted. Taking the axial center shift of the respective upper and lower supports 119A and 119B into consideration, it is extremely hard to reduce the gap between the bar 117 and the respective upper and lower supports 119A and 119B. This can not completely eliminate the noise depending on the situations.
Furthermore, in the bar supporting apparatus which supplies a large amount of oil and causes the bar to float by the supplied oil, the large amount of oil is used to enable rotation without noise even if the rotating bar oscillates, but the oil may disadvantageously spatter when the large amount of oil is supplied from an oil supplying device provided to the large hydraulic unit to the respective supports. Accordingly, it is necessary to manufacture an apparatus which is entirely covered with a cover so that the spattered oil is collected to be returned to the hydraulic unit for circulation, which may result in the expensive bar supporting apparatus.
It is an object of the present invention to provide a bar supporting apparatus which can accurately match axial centers of plural supports supporting a rotating bar with each other on the same axial center at the rear of a main spindle of an automatic lathe and which can be inexpensively manufactured.
To achieve this aim, the present invention provides a bar supporting apparatus for preventing a bar which is griped by a chuck of a main spindle of an automatic lathe and rotates at the rear of the main spindle from oscillating, the apparatus comprising: a case into which the bar is inserted along its longitudinal direction; and a support for supporting the bar, wherein a through hole into which the support is inserted is formed on the side surface of the case, and the support is inserted from the through hole into the case so that the support is fixed to the case with the outer surface of the case as a proof.
With this structure, when a plurality of through holes are formed to the case in the longitudinal direction thereof at predetermined intervals, the supports whose number is equal to that of the through holes can be attached. Therefore, the bar inserted into the case can be supported from one end to the other end at predetermined intervals. Further, when all reference faces of the case to which a plurality of supports are fixed are set out and a part from the axial center of the supporting portion of support for supporting the bar to the reference face of the support fixed to the case is set out, the axial centers of the supports supporting the bar among the plurality of supports attached in the longitudinal direction of the case can have the same axial center. This is extremely practically effective.
In addition, when the external diameter of the bar is changed, since the support is inserted from the through hole formed to the side surface of the case into the case to be fixed therein, only the support which is fitted to the external diameter of the bar has to be replaced, which extremely facilitates the operation. Thus, although replacement of the case in the prior art is very troublesome, only the supports have to be changed even if the external diameter of the bar is changed when the case is designed for allowing the bar processing maximum diameter of the automatic lathe, thereby greatly improving convenience.
Moreover, the support is inserted from the through hole on the side surface of the case into the case and the outer side of the support is fixed to the case. Although all of the outer periphery on the outer side of the support may not be fixed to the case in some cases, the support becomes like, e.g., a bamboo joint in the case and the bar is supported on the substantial center of the case. Therefore, it is possible to acquire the same effect as that obtained when the supporting portion of the bar is supported by the thick case in particular on the outer side in the circumferential direction, and the bar is supported with the high rigidity. Accordingly, even if the oscillating force is generated by rotation of the bar, it is transferred to the case through the support, and the entire case can normally suppress the force. As a result, although the force for oscillating the case acts, it can be suppressed in the most effective manner. Thus, it is possible to enable rotation without oscillation and noise with oscillating or deflection being prevented from occurring to the case when the bar is deflected to be rotated.
Among the plural supports attached to the case in the longitudinal direction thereof, since the axial centers of the supports supporting the bar can be matched with the same axial center with the high accuracy, a gap between the bar and the supporting portion supporting the bar can be reduced. When the gap is small, a large quantity of oil for generating the dynamic pressure does not have to be supplied between the bar and the supporting portion. Since it is enough if only a small amount of oil, e.g., lubrication oil is supplied, it is not necessary to provide the hydraulic unit and the like in particular. In addition, since the plural supporting portions are accurately arranged on the same axial center even though the gap is small, the bar can be lightly and smoothly rotated. Therefore, a quantity of heat to be generated is very small, and no seizure is generated even if the bar is rotated at a high speed. Additionally, it is possible to greatly minimize the vibration or oscillation of the bar when the bar rotates at a low speed to a high speed.
Moreover, the bar is not exposed to the outside because the rotating bar is supported in the case. This can avoid the possible danger that, for example, a cloth is intertwined with the rotating bar. Also, oil stained on the surface of the bar and the lubrication oil supplied to the supporting portion can be prevented from spattering to the outside of the case even if a cover and the like is not used. Thus, the bar supporting apparatus can be very safely used.
Here, the bar supporting apparatus is provided with a fixing member for fixing the support, and the fixing member is preferably fixed to the external surface of the case with the support being inserted from the through hole into the case.
In this case, it is easy to accurately finish the external surface of the case by cutting and the like. By using the external surface of the case as a proof/reference surface and positioning the bearing surface of the support, the bearing surfaces of all the supports can be arranged on the coaxial center and matched with the axial center of the case. This can facilitate setting out of a part from the external surface of the case to the bearing surface of the support even if the support is replaced. Therefore, the oscillation of the rotating bar can be minimized by reducing dimensional irregularities from the external surface of the case to the bearing surface of the supports. Consequently, the bar can rotate at a high speed to greatly improve the productivity.
In particular, it is preferable to form irregularities for positioning between the fixing member and the case. As the irregularities for positioning, it is preferable to use a positioning pin and a positioning hole or an engagement projection and a groove. In this case, when the positioning pin is inserted into the hole, the fixing member is positioned at a predetermined location of the case, and the axial centers of the respective supports can be further accurately and easily matched with each other. Further, in case of the projection and the groove, by only engaging the engagement projection on the inner surface of the fixing member with the groove on the outer surface of the support and then engaging the engagement projection with the groove on the external surface of the case, the fixing member and the support can be attached along the engagement projection of the case. This enables the support to be fixed to the case in a short time. Therefore, the bar supporting apparatus can be rapidly and extremely easily assembled. On the contrary, when the engagement projections are formed on the external surface of the case and that of the support and the groove is formed on the internal surface of the fixing member, the similar effect can be obtained. On the other hand, the internal surface of the fixing member, the external surface of the case and the external surface of the support may be smooth surfaces. In this case, since the engagement projection or the groove do not have to be formed, a number of processing steps of the bar supporting apparatus can be reduced as compared with the case where these members are formed.
In addition, it is preferable that the case has a tubular shape, the external surface of the support is bent with a curvature substantially equal to that of the external surface of the case and the internal surface of the fixing member is formed on a curved surface which is bent with a curvature substantially equal to that of the external surface of the case. In this case, since the external surface of the case having a tubular shape and the external surface of the support are fittingly fixed on the circumference of the cylinder with the same curvature, the axial center of the external surface of the case and that of the external surface of the support are matched with each other. Therefore, it is possible to set out the bearing surface of the support in such a manner that the axial centers of the bearing surfaces of the supports supporting the bar are matched with the axial center of the external surface of the case. Consequently, for example, when the external surface of the case is processed so as to provide the cylindrical straightness, the axial centers of the plural supports attached to the case in the longitudinal direction thereof and the axial center of the case can be matched with the same straight axial center. Therefore, the gap between the bar and the bearing surface of the support can be minimized, thereby greatly reducing the oscillation of the rotating bar.
On the other hand, the case may have a prismatic shape and the external surface of the support and the internal surface of the fixing member may have a shape substantially equal to that of the external surface of the case. In this case, the position from the external surface of the case to the bearing surface of the support can be easily set out. As a result, by processing the external surface of the case into a flat surface with the high accuracy, the axial center of the case and the centers of the opposed supports provided in the longitudinal direction at predetermined intervals can be matched with the same axial center. Therefore, the gap between the bearing surfaces of the opposed supports and the bar can be reduced, and the oscillation of the rotating bar can be significantly decreased.
In addition, the case may have a prismatic shape, and a through hole may be formed to an angular portion of the case. The external surface of the support may protrude with the substantially same shape as that of the external surface of the angular portion of the case, and the internal surface of the fixing member may be formed into a shape substantially fitted to the external surface of the angular portion of the case, i.e., a concave shape. In this case, the bearing surface of the support can be set out with the external surface forming the angular portion of the case as a reference. With this arrangement, for example, the center of the bearing surfaces of the opposed supports can be substantially matched with the axial center of the case from the angular portions. Therefore, by accurately finishing the external surface of the case, it is possible to accurately arrange the axial center of the case and the center of the opposed supports in the longitudinal direction at predetermined intervals on the same axial center. This can reduce the gap between the bar and the supports, and the oscillation of the bar can be greatly suppressed.
Here, in the bar supporting apparatus, it is preferable that the through holes are formed on the opposed side surfaces of the case and the respective supports are inserted from these through holes into the case so that the bar can be supported from the both sides. In this case, with the accurately finished external surface of the case being used as a reference, the rotating bar can be accurately supported by the opposed supports on the internal surface of the case. Consequently, the axial center of the external surface of the case can be matched with the axial centers of the supporting portion to form the supporting portion even if the supports are replaced. Therefore, when the supports are moved by the power of, for example, a pneumatic cylinder and the like, the supporting portion can be automatically opened/closed. Even if the oscillation of the bar having a different external diameter is supported, the supports associated with the bar can be rapidly substituted, thereby significantly improving the convenience.
In particular, the bar can be automatically supplied from an opening by providing an opening which is formed along the longitudinal direction of the case and notched so as to enable insertion and removal of the bar, a bar pedestal installed at a position slightly lower than the position where the bar is supported by the supports, and a supplying device capable of mounting the bar on the bar pedestal. Therefore, the convenience of the bar supporting apparatus can be greatly improved. Further, since the bar pedestal provides a small gap below the bar when the bar is supported by the supports, it is possible to prevent the bar from contacting with the bar pedestal even if the rotating bar oscillates in some measure.
Moreover, the through holes may be formed on the opposed side surfaces of the case, and the supports may be inserted into the case from one through hole to the other through hole. Also, the supporting portion into which the bar is inserted may be formed to the supports. In this case, the supports can be simply manufactured in particular. This can cause the axial center of the external surface of the case to be matched with the axial center of the supporting portion by only inserting the support from one through hole to be fixed. Therefore, a number of processing steps of the bar supporting apparatus can be greatly reduced to enable the inexpensive manufacture.
In addition, the through hole may be formed on one side surface of the case so that the support can be inserted from the through hole into the case, and the supporting portion into which the bar is inserted may be formed to the support. In such a case, the support can be further simply manufactured. As a result, the axial center of the external surface of the case can be matched with the axial center of the supporting portion by only inserting the support from the through hole to be fixed, and a number of processing step of the bar supporting apparatus can be significantly reduced to enable the inexpensive manufacture.
Further, in this case, there may be provided on the internal surface of the case at a position opposed to the through hole a fixing portion consisting of a recession to which an end portion of the support inserted into the case is fitted. According to this structure, the fixing portion can be formed with the equal accuracy as the external surface of the case, and the support can be positioned by the fixing portion.
Furthermore, a plurality of through holes may be formed in parallel to the longitudinal direction of the case. This can facilitate processing of the case.
Moreover, a plurality of through holes may be formed on the side surface of the case along the longitudinal direction thereof, and an angle of each through hole seen from the center of the case may be shifted from each other. The respective supports may be inserted from these through holes into the case to support the bar. In this case, the bar inserted into the case can be supported by the support at a position shifted in the circumferential direction. This can avoid the inconvenience such that the end of the support having the lower strength is deformed due to the stress caused by the oscillation of the rotating bar. Therefore, the support can be prevented from being damaged, thereby attaining the very long duration of life.
It is preferable that an engagement projection is formed on one of the internal surface of the fixing member or the external surface of the case and the external surface of the support and a groove engaging with the engagement projection is formed on the other of them. For example, the engagement projection is formed on the internal surface of the fixing member, and the groove engaging with the engagement projection is formed on the external surface of the case. Also, the groove engaging with the engagement projection is formed on the external surface of the support.
Further, an elastic member may be preferably provided between the fixing member and the support. In this case, an impetus can be given to the bar inserted to the supporting portion in a direction of the axial center of the case. Consequently, for example, even if the bar having a relatively large diameter and a curve and the like is bent and rotates to generate a large oscillation, the force to give impetus of an impetus giving member can suppress the large oscillation of the bar. Therefore, the vibration or the noise of the rotating bar can be prevented from occurring.